1. Field of the Invention
The present invention relates to a chemical amplification type resist composition for use in microfabrication of semiconductor.
2. Prior Art
Semiconductor microfabrication employs a lithography process using a resist composition. In lithography, theoretically, the shorter the exposure wavelength becomes, the higher the resolution can be made, as expressed by Rayleigh's diffraction limit formula. The wavelength of an exposure light source for lithography used in the manufacture of semiconductor devices has been shortened year by year as g-line having a wavelength of 436 nm, i-line having a wavelength of 365 nm, KrF excimer laser having a wavelength of 248 nm and ArF excimer laser having a wavelength of 193 nm. F2 excimer laser having a wavelength of 157 nm seems to be promising as the next-generation exposure light source. Further, as the exposure light source of the subsequent generation, soft X ray (EUV) having a wavelength of 13 nm or shorter has been proposed as the exposure light source following the 157 nm-wavelength F2 excimer laser. As a somewhat different type of lithography technology from above, the electron beam lithography has been intensively studied.
As the resists suitable for such light sources, the chemical amplification type resists utilizing chemical amplification effect of acid catalysts have been proposed. When a chemical amplification type resist is radiated, an acid is generated at the radiated part from acid generator in the resist, and then the solubility of the resist at the radiated part to alkali developing solution changes by heat treatment called as post exposure bake, which may hereinafter be abbreviated as PEB, and thereby the resist provides positive or negative patterns.
For a chemical amplification type positive resist, a resin in which an alkali soluble group is protected by a group to be cleaved by the action of an acid is frequently used in combination with an acid generator. It has been reported that high resolution and good dry etching resistance are acquired when a protecting group such as 2-alkyl-2-adamantyl group or 1-adamantyl-1-alkylalkyl group is used as the group to be cleaved by the action of an acid (for example, JP 9-73173-A, S. Takechi et al., J. Photopolym. Sci. Technol., Vol. 9, No. 3, 475-487 (1996) etc.). In addition, a resist for electron beam utilizing a copolymer of 2-methyl-2-adamantyl methacrylate or 2-ethyl-2-adamantyl methacrylate and hydroxystyrene is presented and, in particular, a resist for electron beam utilizing a copolymer of 2-ethyl-2-adamantyl methacrylate and hydroxystyrene has been reported to have high sensitivity, good etching resistance and high resolution in KrF excimer laser exposure (for example, Nozaki et al., J. Photopolym. Sci. Technol., Vol. 13, No. 3, 397-403 (2000)).
In electron beam lithography, however, sensitivity is low and throughput in production of an integrated circuit is problematic when these resists are used as they are. In this respect, it is desired to acquire high sensitivity for resist. However, in general, when sensitivity of resist is enhanced, resolution deteriorates, and smoothness of pattern shape as well as pattern profile (edge roughness) becomes poor. Since large edge roughness of pattern exerts an influence on accuracy of microfabrication, the edge roughness is desired to be smooth. Thus, the results obtained with conventional resists cannot meet desirable performances in sensitivity, resolution, pattern shape and the like.